Abstract:We report astonishingly high transmission enhancement factors through a subwavelength aperture at microwave frequencies by placing connected split ring resonators in the vicinity of the aperture. We carried out numerical simulations that are consistent with our experimental conclusions. We experimentally show higher than 70,000-fold extraordinary transmission through a deep subwavelength aperture with an electrical size of λ/31×λ/12 (width × length), in terms of the operational wavelength. We discuss the physical origins of the phenomenon. Our numerical results predict that even more improvements of the enhancement factors are attainable. Theoretically, the approach opens up the possibility for achieving very large enhancement factors by overcoming the physical limitations and thereby minimizes the dependence on the aperture geometries. ©2010 Optical Society of AmericaOCIS codes: (160.3918) Materials: Metamaterials; (050.1220) Diffraction and gratings: Aperture. References and links1. H. A. Bethe, "Theory of diffraction by small holes," Phys. Rev. 66(7-8), 163-182 (1944). 2. T. W. Ebbesen, H. J. Lezec, H. F. Ghaemi, T. Thio, and P. A. Wolff, "Extraordinary optical transmission through sub-wavelength hole arrays," Nature 391(6668), 667-669 (1998)

Cataloged from PDF version of article.In this paper, we present a new analytical model of\ud the connected bi-omega structure consisting of two bi-omega particles\ud connected together through their arms. A single bi-omega\ud particle consists of a pair of regular equal omegas with mirror\ud symmetry. Assuming the individual bi-omega particle electrically\ud small, the equivalent circuit is derived, in order to predict its\ud resonant frequency. Then, two bi-omega particles are connected\ud together, obtaining a symmetric structure that supports two\ud fundamental modes, with even and odd symmetries, respectively.\ud The proposed analytical model, then, is used to develop a procedure\ud allowing the design of the particle for a desired resonant\ud frequency. The effectiveness of the proposed analytical model and\ud design guidelines is confirmed by proper comparisons to full-wave\ud numerical and experimental results. We also demonstrate through\ud a proper set of experiments that the resonant frequencies of the\ud connected bi-omega particle depend only on the geometrical and\ud electrical parameters of the omegas and are rather insensitive to\ud the practical scenario where the particle itself is actually used, e.g.\ud in free-space, rectangular waveguide or across an aperture in a\ud metallic screen

Enhanced transmission through circular and rectangular sub-wavelength apertures using omega-shaped split-ring resonator is numerically and experimentally demonstrated at microwave frequencies. We report a more than 150,000-fold enhancement through a deep sub-wavelength aperture drilled in a metallic screen. To the authors' best knowledge, this is the highest experimentally obtained enhancement factor reported in the literature. In the paper, we address also the origins and the physical reasons behind the enhancement results. Moreover, we report on the differences occurring when using circular, rectangular apertures as well as double-sided and single-sided omega-like split ring resonator structures

We report strong near-field electromagnetic localization by using subwavelength apertures and metamaterials that operate at microwave frequencies. We designed split ring resonators with distinct configurations in order to obtain extraordinary transmission results. Furthermore, we analyzed the field localization and focusing characteristics of the transmitted evanescent waves. The employed metamaterial configurations yielded an improvement on the transmission efficiency on the order of 27 dB and 50 dB for the deep subwavelength apertures. The metamaterial loaded apertures are considered as a total system that offered spot size conversion ratios as high as 7.12 and 9.11 for the corresponding metamaterial configurations. The proposed system is shown to intensify the electric fields of the source located in the near-field. It also narrows down the electromagnetic waves such that a full width at half maximum value of λ/29 is obtained.

In this contribution, we review our recent work on the extraction of the electromagnetic power from electrically small apertures by using metamaterial-inspired resonators. First, we present an antenna interpretation of the power transmission through sub-wavelength apertures and discuss the questioned concept of 'enhanced transmission'. Then, we present the so-called 'connected bi-omega particle' and the related analytical model. After that, exploiting proper numerical and experimental examples, we also show that the electromagnetic response of such a particle is not influenced by the surrounding environment. This unique property makes the particle a suitable candidate for the implementation of microwave components based on the selective power extraction from electrically small apertures. Finally, the application of the proposed concepts to the design of innovative microwave components, such as waveguide filters, diplexers, power-splitters, modal filters, horn antennas, etc. will be considered and demonstrated through proper numerical and experimental results. © 2012 IEEE